The background description provided herein is for the purpose of generally presenting the context of the present invention. The subject matter discussed in the background of the invention section should not be assumed to be prior art merely as a result of its mention in the background of the invention section. Similarly, a problem mentioned in the background of the invention section or associated with the subject matter of the background of the invention section should not be assumed to have been previously recognized in the prior art. The subject matter in the background of the invention section merely represents different approaches, which in and of themselves may also be inventions. Work of the presently named inventors, to the extent it is described in the background of the invention section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.
Low cost, light-weight, safe, and durable energy storage devices and systems are in high demand as the global society is making a quick transition into clean energy and energy saving modes of living. While there are many options of generating clean energy such as solar, wind, and geothermal, there is also a big need for energy storage systems for transportation and local utility usage. This is part of the larger equation of how to reduce loss, such as long distance transmission of electricity, and conserve the use of energy.
To date, most of the energy storage systems are based on electro-chemical (EC) processes which stores and converts energy between electrical and chemical forms. For these systems to function efficiently and safely in a durable manner, decades of devoted research and development have been carried out. A survey of the literature has shown that carbon based electrode has been most studied due to its stability, durability, and chemically easy to work with. Above all, carbon is abundant, light and inexpensive.
Carbon comes in many allotropic forms, such as graphite, diamond, fullerenes, and carbon nanotubes and ropes, etc. Researchers have studied and used various combinations of these carbonaceous materials for the design and operation of electrodes for chemical devices. Carbonaceous materials such as graphite [14, 15] carbon black, [16] activated carbon [17], hard carbon sphere [18], carbon nanotube [19], fullerene and graphene [20], have been used as the catalytic materials. These carbonaceous materials show good electrochemical activity, and among them, carbon black holds the best performance [21]. However, in order to achieve comparable electrochemical performance as platinum, a thick (about 15 μm) carbon black layer is required as shown recently by Murakami et al. [21]. Cells fabricated with carbon black resulted in about 25% less energy conversion efficiency as compared to the platinized CE.
To improve this situation, it is necessary to further increase the surface to volume ratio of the carbon nano species as well as the edge surface area to basal surface area ratio of the carbon nano material [22]. The challenge is how and has not been answered satisfactorily yet.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.